Other than a dead straight putt, all putts aimed directly at the hole tend to move away from the hole as the putt slows on a planar green (sloped back-to-front). That movement will be either left-to-right or right-to-left, depending on which side of the Zero Line (the straight putt line, either uphill or downhill, per Aim Point theory http://www.aimpointgolf.com/aimpointtv.html.